Condensing Side-Arm Water Heater

ABSTRACT

An apparatus for providing a condensing side-arm water heater with improved efficiency. The condensing side-arm element recirculates exhaust gases into heating the cooler part of a water heater tank by the thermosiphon (or buoyancy) effect in a counterflow configuration, thus increasing efficiency of the water heater.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority as a continuation application to PCTInternational Patent Application No. PCT/US2007/072160, filed Jun. 26,2007, which in turn claims priority to U.S. Provisional PatentApplication Ser. No. 60/805,811, filed Jun. 26, 2006, both of which arehereby incorporated in their entireties by reference.

STATEMENT REGARDING FEDERAL FUNDING

This invention was made with U.S. Government support under ContractNumber DE-AC02-05CH11231 between the U.S. Department of Energy and TheRegents of the University of California for the management and operationof the Lawrence Berkeley National Laboratory. The U.S. Government hascertain rights in this invention.

REFERENCE TO A COMPUTER PROGRAM

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to water heating, and morespecifically to high efficiency water heating, and most specifically tocondensing side-arm water heaters.

2. Description of the Relevant Art

Both gas and electric water heaters are well known. It is believed thatcondensing side-arm gas-fired water heaters has not been done. Such adevice dramatically increases the efficiency of water heating at lowcost.

BRIEF SUMMARY OF THE INVENTION

In one embodiment, this invention provides for a condensing side-armwater heater, comprising: a) a tank; b) a recirculation pipe fluidlyconnected to an upper and lower aperture in the tank; c) a heatexchanger in thermal contact with the recirculation pipe; d) a burnerfor heating the water, that produces heated combustion products; e) anexhaust system that takes the heated combustion products from theburner, and transfers a fraction of the heat to the heat exchanger; i)the exhaust system comprising: (1) an exhaust fan blower; (2) a drippipe; (3) and an air inlet; f) whereby the heated combustion productspass through the exhaust system, condensing water vapor from thecombustion byproducts, and expelling the condensed water vapor throughthe drip pipe. It should be noted that the burner may burn anything thatproduces heat when oxidized in air, examples would include, oil, gas, LPgas, propane, etc.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention will be more fully understood by reference to thefollowing drawings, which are for illustrative purposes:

FIG. 1 is a traditional electric water heater schematic.

FIG. 2 is a condensing side-arm gas-fired water heater.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Definitions

“Side-arm” means external to a main reservoir tank, physically appearsas an arm on the side.

Introduction

In this application methods for increasing the efficiency of combustedwater heating through use of the combustion byproduct heat.

This invention would be a condensing sidearm heat exchangersynergistically attached to a water heater tank. The heated water wouldbe transferred from a side-arm heat exchanger to the tank bythermosiphonic action, or through heat-induced density changes in thewater acting as a driver. No mechanical pumps would be necessary. Thewater tank could be an electric resistance tank with the elementsremoved.

To retrofit an existing gas water heater, the sidearm heater could beplumbed into the openings where the original elements had previouslybeen placed.

For highest efficiencies, the heat exchanger would have sufficient heattransfer so as to condense the water vapor present in the combustionproducts. The combustion products would be too cool to buoyantlyself-vent, so an electric fan would be used to vent the combustionproducts. By using a fan, the combustion products could be pulled downthrough the heat exchanger. The bottom of the heat exchanger would beconnected to the lower end of the tank. The combustion products wouldexit the heat exchanger at the lower end where they would be cooled bythe coldest water in the tank. By using thermosiphon action to transferheated water to the tank, the flow rate will be slow enough to preservestratification in the tank. This keeps cold water in the bottom of thetank even as the rest of the water in the tank heats up.

Because the combustion products exit the heat exchanger where the coldwater enters, the heat transfer efficiency is high, as is usually thecase in counterflow heat exchangers. This will maximally cool thecombustion products and condense as much of the water vapor in thecombustion products as possible. The combustion products are cool enoughso they can be vented to the outdoors through an attached plastic pipe.Inlet air can be drawn in through plastic pipe from outdoors as well.This would be an isolated combustion system thereby removing accidentalsources of ignition of flammable vapors. Flammable vapor ignitionresistant designs will not have to be used on this water heater. If theburner is made small enough (perhaps as low as 15 kBtu/hr), the motor onthe draft inducer fan can be powered with low-voltage electricity. Thiswould enable installers to provide power to the water heater withoutneeding the services of an electrician.

Because combustion is fan assisted, it may be possible to use one of thelow NO_(x) burners that Robert Cheng et al. of U.S. Pat. No. 5,879,148have invented. Thus, not only would the water heater be much moreefficient than current water heaters, it would also have much loweremissions. There would be two thermostatic controls on the water heater.One, near the top of the heat exchanger would decrease the resistance towater flow through the heat exchanger as the temperature rises. Thiscontrol would allow water to move through the heat exchanger morequickly, so that it acquires less heat and enters the water heater at atemperature that is not quite so hot. Conversely, the thermostaticcontrol would increase resistance to water flow as temperature drops.This control will keep the heated water in the top of the tank at aconstant temperature. The other thermostatic control would be at thebottom of the heat exchanger. When the water temperature at this pointrises above a setpoint, gas flow to the burner would be stopped, andthen the draft inducer fan would be turned off. When the watertemperature at this point gets cool enough, the fan, igniter and burnerwould all be started.

This invention allows water to be heated much more efficiently (˜90%compared to current typical water heater efficiencies of 60%).

The temperature of water in the heat exchanger does not increase untilthe tank is full of hot water.

Embodiments of the Condensing Side-Arm Water Heater

Refer now to FIG. 1, which shows in a cut away view a few of the salientfeatures of a prior art electrical water heater 100. The electricalwater heater 100 has an interior heated space 110 that is typicallyfilled with water. The heated space 110 is substantially surrounded byinsulation 120. An upper electrical heating element 130 and lowerelectrical heating element 140 provide heat to the heated space 110, andare inserted through and secured to the upper threaded aperture 150 forthe upper element 130, and the lower threaded aperture 160 for the lowerheating element 140.

It should be noted that for optimal operation, the heat exchanger/burnerassembly lower threaded aperture 160 should be mounted as low aspossible on the tank, perhaps even extending below the bottom of thetank (which is not shown in FIG. 1). Of course in the case ifretrofitting an electrically heated tank, this is difficult orimpossible to achieve.

Although here we initially discuss retrofitting an electrical waterheater, the invention disclosed here could be made from non-electricalwater heater components, and suitably combined.

FIG. 2 shows a side-arm condensing water heater 200 based on theretrofitting or new construction of the electrical water heater 100 ofFIG. 1. In the side-arm system 200, an interior space 205 is filled withwater, which is insulated from external temperatures by insulation 210.In this instance, the upper 130 and lower 140 electrical water heatingelements have been removed. Instead, a recirculation line 215 forms aloop between the upper aperture 270 and the lower aperture 275, whichmay have contained the upper 130 and lower 140 electrical water heatingelements from FIG. 1, or may just be new apertures in a tank as built.

The recirculation line 215 has surrounding it heat transfer elements 220that are in good thermal contact with the recirculation line 215. Asupply of air enters through aperture 225, to provide oxidizer to aburner 230. Combustion byproducts are pulled down through the heattransfer elements 220, and pulled through an exhaust pipe 235 that pumpsthe exhaust byproducts to an exit vent 250 by virtue of a fan blower240. One of the combustion byproducts is that of condensed water vapor,which drips onto a collection area 255 below the heat transfer elements220. The condensate is then exhausted through a drip pipe 260. Aninsulated housing 265 surrounds the heat transfer elements 220, and theburner 230. The insulated housing 265 is attached to the insulation 210of the interior space 205.

Power for the fan blower 240 may be supplied externally, though maybetter be provided by a thermopile supply 280 that would be mounted inclose proximity to the burner 230. Wires are not shown to the fan blower240, as such wiring would be obvious.

Operation of the system is controlled by an upper thermostat at 270 andlower thermostat at 275.

This invention is intended as a replacement for currently existingresidential gas water heaters.

CONCLUSION

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication or patent application were eachspecifically and individually indicated to be incorporated by reference.

The description given here, and best modes of operation of theinvention, are not intended to limit the scope of the invention. Manymodifications, alternative constructions, and equivalents may beemployed without departing from the scope and spirit of the invention.

1. A condensing side-arm water heater, comprising: a) a tank; b) arecirculation pipe fluidly connected to an upper and lower aperture inthe tank; c) a heat exchanger in thermal contact with the recirculationpipe; d) a burner for heating the tank, that produces heated combustionproducts; e) an exhaust system that take the heated combustion productsfrom the burner, and transfers a fraction of the heat to the heatexchanger; i) the exhaust system comprising: (1) an exhaust fan blower;(2) a drip pipe; (3) and an air inlet; f) whereby the heated combustionproducts pass through the exhaust system, condensing water vapor fromthe combustion byproducts, and expelling the condensed water vaporthrough the drip pipe.
 2. The condensing side-arm water heater of claim1, comprising: a) an upper and lower thermostat that allow control ofthe condensing side-arm water heater.
 3. The condensing side-arm waterheater of claim 1, comprising: a) an insulating material disposed aboutthe exhaust system, so as to increase thermal efficiency.
 4. Thecondensing side-arm water heater of claim 1, wherein the burnercomprises: a) a low NO_(x) burner.
 5. The condensing side-arm waterheater of claim 4, wherein the low NO_(x) burner comprises: a) acombustion zone; b) a pilot mounted adjacent to said combustion zone,including, c) a mixer for premixing fuel and oxidant to produce a feedgas; d) a mechanical swirler located downstream from said mixer andcapable of receiving a premixed feed gas from said mixer, said swirlerincluding i) a central passage having an entrance for accepting aportion of said feed gas, a flow balancing insert that introducesadditional pressure drop beyond that occurring in the central passagewithout said flow balancing insert, and an exit aligned to direct saidportion of said feed gas into a second combustion zone, and ii) anannular passage about said central passage having an entrance foraccepting a second portion of said feed gas, one or more vanes orientedto impart angular momentum to feed gas exiting said annular passage andan exit aligned to direct said second portion of said feed gas into thesecond combustion zone, wherein said swirler does not inducerecirculation in said feed gas, and wherein said second combustion zoneis capable of supporting combustion of said premixed feed gas; andwherein said pilot is capable of igniting a fuel mixture provided tosaid combustion zone.